Yarn and fabric having improved pill resistance



A ril 15, 1969 J. F. RYAN, JR 3,438,192

YARN AND FABRIC HAVING IMPROVED PILL RESISTANCE Filed Sept. 28. 1966 INVENTOR JAMES FRANCIS RYAN, JR.

4' ,1 J, BY

ATTORNEY United States Patent 01 hoe 3,438,192 Patented Apr. 15, 1969 U.S. Cl. 57--140 11 Claims ABSTRACT OF THE DISCLOSURE Low strength acrylic fiber having, upon boil-off, a substantially straight configuration and specific shrinkage characteristics. The fibers are prepared by Washing and drawing freshly spun acrylic filaments, and plasticizing them under restraint to relax the filaments. This fiber, combined with high strength, high-shrinkage fiber, is used to provide pill-resistant, bulked, composite yarns and fabrics thereof, having excellent aesthetics.

This application is a continuation-in-part of my copending application S.N. 480,730, filed Aug. 18, 1965, now abandoned, which in turn is a continuation-in-part of my copending application S.N. 307,822, filed Sept. 10, 1963, now abandoned.

This invention relates to improved acrylic staple and tow and to structures of superior tactility and freedom from surface distortion made therefrom.

Fibers of acrylonitrile polymers are more wool-like than most other synthetic fibers. They have many advantages over wool such as the ability to be washed without shrinking, resistance to insects, and the capacity of being easily dyed to bright and fast shades.

Some animal fibers have a superior smooth tactility which is in large measure due to freedom from sharp bends or crimp. Such a fiber is difficult to process in ordinary textile manufacturing due to deficiency in the interfiber cohesiveness needed in the early staple processing steps such as picking, carding and first drafting. Such fiber frequently is lost to an excessive degree from its fabrics (sheds excessively) for the same reason. Moreover, the most luxurious smooth-tactility fibers, such as mohair and cashmere, have natural surface modifiers which soften the fiber, providing a someWhat slippery feel. This combination of straightness and surface modification accounts for the substantial advantage of certain natural fibers over synthetic fibers in commercially important, luxury markets, despite the practical disadvantages resulting from low interfiber cohesiveness. It would be highly advantageous to combine the luxurious characteristics of certain animal fibers with the superior durability and carefree utility of the acrylic fibers.

The acrylontrile fibers used heretofore in classic knit sweaters resulted in sweaters that exhibit surface distortion (develop pills) as the result of the abrasive action encountered during wear. Pills are small balls or fluffs of fibers which are rather tenaciously held on the surface and thereby detract from the attractiveness of garments. The acrylontrile fibers have also lacked the smooth slick feel of some natural fibers.

Many efforts have been made to overcome the pilling of synthetic fibers. Pilling can be decreased by highly twisting the yarns, but this greatly decreases the bulk and cover, and strongly modifies the aesthetics of knit fabrics. Both lubricating and slip-proofing finishes have been tried with only slight improvement. Furthermore, any such improvement is only temporary since finishes with such characteristics which are generally available are removed by only a few washings or dry cleanings.

The blending of lowand high-shrinkage fibers to obtain bulky yarns and fabrics is not new, and is taught, for example, in U.S. Patents 2,810,281 and 2,985,940. However, fabrics made from such blends, especially bulkyknit fabrics, heretofore have suffered from pilling and from a lack of smoothness and slickness. For these reasons the use of such blends has been limited.

Likewise, bulky fabrics have been made from composite fibers. These are fibers spun from two different polymers or copolymers in a side-by-side or sheath-core relationship along the length of the fiber; they differ from homo-fibers which are spun from a single polymer or copolymer in that because of an established difference in shrinkability between the two components of the composite fiber, they develop a spiral crimp on boil-off in water, for example, which results in bulky yarns and fabrics. One method of preparing such fibers is described in U.S. Patent 3,038,236. But such fibers yield fabrics which are not optimum for many uses because of severe pilling and harsh tactile qualities.

The present invention provides acrylic staple having good textile processibility, and exceptional straightness in the final structure and a process for producing the fiber. It further provides a straight fiber with durable soft-slick tactility. It still further provides bulky knit fabrics of acrylic fibers having in combination the fine aesthetics of animal fibers and relative freedom from pilling during normal wear. It also provides novel composite yarn which is especially suitable for preparing knit fabrics of the foregoing qualities.

These and other advantages are attained in an acrylic staple having, preferably, a temporary and a permanent configuration, the temporary configuration comprising 3 to 15 crimps per inch for good textile processibility, the permanent configuration being developed from the temporary configuration by boil-off in water and being characterized by a straightness factor, SF, of 0.70 to 1.50, an initial shrinkage temperature, IS, of at least 145 C., and by a maximum shrinkage force factor, MSF, of no more than 0.9.

By forming yarn blends that include at least 25 weight percent of such fiber, the unique utility of the fiber can be attained in the blend. These yarn blends can be bulked in skein or fabric form, and in either practice the defined staple becomes the predominant surface fiber. In general this acrylic staple is produced by spinning acrylic filaments, simultaneously washing the spun filaments to reduce spinning solution solvent to below about 5 percent and drawing to to 450 percent, preferably 120 to 300 percent, of the as-spun length, relaxing the drawn filaments to the extent of 2 to 40 percent, preferably 15 to 40 percent, of the drawn length by exposure to plasticizing conditions for at least 0.5 second while restrained by a force of at least 5 milligrams per denier (mg/den), optionally mechanically crimping at a temperature no higher than 20 C. below the T of the fiber to 3 to 15 crimps per inch and removing any plasticizing material. In this specification the term acrylic staple means staple 3 comprising at least 85 percent by weight of polymerized acrylonitrile in the polymer. It will be seen that the plasticized taut relaxation is an important element of the processing sequence leading to new acrylic fibers which provide the lasting luxurious surface characteristics desired in classic knit sweaters.

The properties of the acrylic staple in the second or permanent state are determined on the staple that is drawn, relaxed as described and crimped to 3 to 15 crimps per inch.

The straightness factor, SP, is determined as follows:

(1) Approximately one gram of the staple to be tested, having a cut length of approximately 3 inches (7.6 cm), is hand-carded.

(2) 0.5 gram of the fiber is accurately weighed.

(3) Approximately 250 ml. distilled water is placed in a 400 ml. beaker, and the weighed sample of fiber is dropped onto the surface of the Water in as open a manner as possible. It may be necessary at this point, particularly if a hydrophobic surface modifier is present, to add a few drops of a wetting agent to assure complete wetting of the sample.

(4) The beaker is covered with a watch glass and immersed completely in a steam bath for 40 minutes.

(5) The beaker is removed from the steam bath and allowed to cool to 30 C. or lower.

(6) The sample is removed from the beaker with a glass rod, laid on a paper towel without distorting its configuration, and allowed to dry.

(7) Eight clumps of filaments are selected at random from the dried fiber and laid on a black velvet surface. One filament is selected from each bundle.

(8) Pieces of masking tape are cut to a size which Weigh 2 mg./denier (calculated on the filament to be tested). One piece is attached to each end of each of the 8 selected filaments.

(9) One of the pieces of masking tape, with the filament attached thereto, is attached to one end of a microscope slide. The filament is permitted to hang under the weight of the second piece of masking tape, and then the second piece of masking tape is attached to the microscope slide. A piece of flat, flexible film having reference marks one-inch apart is placed on the filament. The filament is examined under the microscope by comparing it with inscriptions on a transparent overlay representing Partial Circles Of A, la, /16, 122, %4, V128, /256, and /508 inch radii, coded 8 through 1, respectively.

(10) Each of the curvature found within a one-inch length of the fiber sample is matched with one of the standard curvatures on the overlay and assigned a number code.

(11) The mean curvature of each individual sample of fiber is calculated as the average of the one or more numbers recorded representing the curvatures observed. The number of curvatures observed for each sample is also recorded.

(12) The mean curvature, R, of the overall sample is calculated by averaging the mean curvatures of the eight filaments.

13) The mean frequency, f, of curvatures of the overall sample is calculated by averaging the number of curvatures per inch of filament in the 8 filaments.

(14) The straightness factor SF, is calculated as follows:

R SF f V den.

The initial shrinkage temperature, IS, is determined by mounting a bundle of fibers of about 100 denier between the jaws of an Instron and separating the jaws until a tension of about 0.3 gm. is indicated. With the jaws held at this position, the temperature of the air surrounding the fiber bundle is raised approximately 10 C. per minute. The stress and temperature are recorded as function of time, and a plot of temperature, 1, versus stress is prepared. The temperature, T, at which additional stress first appears is noted on the plot. Initial shrinkage temperature, IS, is calculated as follows:

MSF max. stress (qms) denier of bundle X A yarn blend is provided in one embodiment of the invention which includes at least 25 weight percent of the acrylic staple. I have found that some of the most serious aesthetic limitations of synthetic fibers in apparel and other utility can be overcome by blending with a highly shrinkable fiber, my low shrinkage fiber which, on boilotf, orients as a crimp-free fiber predominantly at and near the surface of the yarn which bulks as the highly shrinkable component retracts. In a preferred embodiment the staple or tow of this invention has an initial mechanical crimp which aids in textile processing but which is lost on boil-off at any convenient stage of processing, as in yarn or fabric form. In a further preferred embodiment, the fiber of this invention is stretched only to to 300% of its as-spun length in manufacture, which imparts low-entanglement tendency.

When these fibers are taut-relaxed as described herein, they exhibit a remarkable resistance to development of crimp. The fibers, can be crimped, as by stuifer-box crimping of the tow before it is cut into staple, while retaining their ability to lose most or all of this crimp during a subsequent hot-wet treatment. Thus, such fibers may be in the crimped state during and spinning but when fabrics containing the fibers aret reated in a hot-wet process, as in dyeing, the crimp will substantially disappear. The straight fibers confer to their fabrics a smooth, slick feel by orienting to the surface of the yarns.

Fibers as normally prepared have, after drawing, a substantial potential shrinkage. When this shrinkage is permitted to occur in an uncontrolled manner, crimp will develop due to the non-uniform drawing stresses always present in the yarn. By allowing shrinkage to occur under a restraint of at least 5 mg./den. and under plasticizing conditions which permit the fiber to shrink, internal stresses are reduced or eliminated without crimping, and the straight configuration remains. Depending on the characteristics of the particular fiber being processed, the conditions required for plasticizing during the relaxation step may be chosen from among passage over heated rolls, hot air, steam of either atmospheric or higher pressure, refluxing organic vapors, vapors from a refluxing mixture of an organic solvent and water, etc. The essential requirement is that the conditions established and the time of exposure be selected such that the fiber will relax to the extent of 2 to 40%, preferably 15 to 40% of its as-drawn length while being restrained by a load of at least 5 milligrams per denier, as, for example, 5 to 30 milligrams per denier.

The second fiber in the blend may be any high-strength fiber which has a relatively high shrinkability. Examples of operable embodiments are found among the acrylic and modacrylic fibers which have been relaxed only partially after drawing or which have been handled in such a way as to retain substantially all of the potential shrinkability developed during the drawing process. Alternatively, a completely relaxed tow may be processed on the Turbo Stapler, Pacific Converter or other such device to a high-shrinkage sliver and blended, without prior relaxation, with the low-shrinkage fiber. For example, a fiber representing a copolymer of acrylonitrile and sodium styrenesulfonate in a ratio of 94/6 to 99/1 is particularly suitable, as are the copolymers of acrylonitrile and a vinyl pyridine, the terpolymers of acrylonitrile, methylacrylate and sodium styrenesulfonate; the modacrylics, which may have substantially more than 15% modification by a nonionic modifier such as vinyl acetate, methyl acrylate, vinylidene chloride, styrene, other vinylactive, copolymerizable monomers, or ionic modifiers such as sodium styrenesulfonate or a vinyl pyridine, and multicomponent, composite filaments prepared in such a Way and being of such a composition as to be self-crimpable on exposure to a "boiling scour also can be used. The essential requirement is that the high shrinkage fiber have sufficient potential shrinkage as it exists in the blend to produce the desired degree of bulking. It is well-known in the art to select a high shrinkage fiber suitable for properties desired in the final yarn or fabric. All the foregoing compositions with the exception of the modacrylics and the composite or bicomponent fibers can be used in preparing any new low-shrinkage staple.

Two types of fibers are blended together to form a single yarn. Blends containing from to 75% of the high-shrinkage fiber and from 90 to 25% of the tautrelaxed fiber have been found satisfactory for the purpose of the present invention. The low-shrinkage fiber concentration is thus about 25% or more. It is important, however, to use enough of the high-shrinkage fiber to re sult in suitable bulking of the low-shrinkage fiber. The preferred ranges for the blends of high-shrinkage fiber and low-shrinkage fiber are to 50% and 85% to 50% respectively.

Blending of the highand low-shrinkage fibers may be accomplished in a variety of ways, such as in the picker or draw frame processing, if both fibers are originally in staple form. Either pin drafting or the Hood Doubler may be more convenient if one of the fibers has previously been processed on the Turbo Stapler or Pacific Converter. The blended slivers are processed into yarn by any avialable means. The resulting yarn may be made into skeins and treated with steam or hot water to shrink and crimp the high-shrinkage fiber, or the yarn may first be knitted into fabrics. In the latter case the the shrinkage will be accomplished during scouring and dyeing of the fabric.

One embodiment of composite yarn produced by the above process is schematically illustrated in FIGURE 1, which represents a longitudinal section of the yarn on an exaggerated scale. Whenever shrinkage occurs, the nonshrinking homofibers are bulked and tend to be pushed to the surface, as illustrated at 1. These fibers do not have the frequent, sharp crimps of the composite fibers 2 making up the core, and, hence, have less tendency to become entangled to form pills. But, more importantly, these surface fibers have the benefit of the taut relaxation of this invention and being substantially straight have a considerably lower tendency to entangle than is characteristic of the crimped fibers. For this reason fabrics made from such yarns have little or no tendency to develop pills. Furthermore, the lack of appreciable crimp in these surface fibers results in :fabrics having a smooth, slick, pleasant tactility.

It will be noted that although I refer to fibers 1 and 2 of FIGURE 1 as the outer sheath and inner core, it will be appreciated that the two types of fiber are not sharply separated in the yarn. The core and sheath fibers blend into each other by a zone of intertwined fibers of both types, which compels the yarn to move or stretch as a unit without physical separation of the sheath from the core.

The yarn blend of this invention yields fabrics which are not only non-pilling but which have good durability to wear, exceeding the durability of comparable fabrics made from natural fibers. By means of this invention, therefore, the combination of high bulk, pleasing aesthetic properties, good durability and freedom from serious pilling problems is attained.

As will be illustrated in the examples, further improvement in the desirable tactility of the fibers, yarns and fabrics of this invention may be obtained by use of a suitable surface modifier. It is known to apply such modifiers which are relatively easily removed by laundering or dry cleaning. It is preferred in the process and product of this invention that the modifier be selected from those which are retained by the fiber through textile processing thereof and through launderings and dry cleanings of the fabrics produced therefrom. A very close approximation of the tactility of animal fibers is obtained by the combination of the exceptionally straight, surface-oriented fiber of this invention and a suitable wash-resistant surface modifier which confers a smooth or slick tactility.

While the fibers of any cross-section may be employed advantageously in the process of this invention, such as for example the usual dogbone and crenulated round fibers, it has been found that an additional improvement in certain aesthetic properties may be obtained by use of a trilobal, or cloverleaf, cross section.

Without limiting this invention, the following examples are given. Percentages and parts are by weight unless otherwise apparent.

EXAMPLE I Part l.A copolymer is prepared containing 96% acrylonitrile (AN) and 4% sodium styrenesulfonate (SSS). The copolymer is dissolved in dimethylformamide (DMF) to give a 27% solution. The solution is dry-spun by a process substantially as described in the Flannagan US. Patent 2,615,198. The resulting filaments are washed in water at C., while being drawn to 2.5 times their spun length, and passed through a chamber containing super-heated steam at C. where 33% relaxation occurs in 3.75 seconds under a tension of 10 mg. per denier to give filaments of 12 denier. A tow of the fibers, with a total denier of 470,000, is then crimped in a stuifer-box crimper to a level of 4.9 crimps per inch and 3.7 crimp index after which it is treated with a commercial lubricating finish. The tow is cut into staple fiber varying in length from 3 to 5 inches. The staple is dried at 130 C. and carded on a worsted card to form a sliver weighing 165 grains per yard (9.8 gms. per meter). This is referred to as Fiber A. This fiber has the following properties:

Straightness factor, SF 0.82 Initial shrinkage temp, IS 165 Maximum shrinkage force factor, MSF 0.3

By omitting the relaxation step while maintaining all other processing steps the same as for Fiber A, a fiber is obtained which has the following properties:

SF 0.58 IS MSF 1.3

Part 2.-Another filament is similarly spun from a terpolymer consisting of 89.6% acrylonitrile, 5.7% methyl acrylate (MA) and 4.7% 2-methyl-5-vinyl pyridine. The washed filaments are drawn to 4 times their spun length yielding filaments of 3 denier. The filaments, as a tow, are crimped in a stuifenbox crimper and then dried in a tunnel oven at C. for 15 minutes. The dried tow is processed on the Turbo Stapler with a hot stretch of 1.78 at a temperature of 138 C. It is cooled, stretch-broken and mechanically crimped to yield a sliver weighing 140 grains per yard (8.3 gms. per meter). This is referred to as Fiber B.

Fiber A has a shrinkage of 1% when boiled ofi. Fiber B has a shrinkage of 40%.

Part 3.Ten slivers of Fiber A are combined with 5 slivers of Fiber B and the combined slivers passed through a Hood Doubler to reduce their maximum staple length to 6 inches or less. Four of the resulting slivers are combined and passed through a pin drafter to form one sliver, and four of the latter type are passed through another pin drafter and finally spun into a 2/9 worsted count yarn having Z turns per inch twist in singles and 2.5 S turns per inch in the ply. Skeins prepared from this yarn are dyed at the boil using both acid and basic dyes so as to dye both fibers. After drying, this yarn is knit on a 3 /2- cut Stoll knitting machine in a half-cardigan pattern.

The dyeing operation at the boil causes the Fiber B to shrink and migrate to the core of the yarn and causes Fiber A to bulk on the surface. The finished fabric is resilient and lofty with a smooth, slick feel. The surface fibers are essentially straight with very little crimp. When tested for pill resistance by ASTM Test D-l375 (ASTM Standards, 1959 supplement, part 10, page 173) a rating of 3.5 is obtained. In this test the number of pills per square inch is determined and the fabrics are rated on a scale from 15, where 5 represents no pilling and 1 represents severe pilling. A fabric with a rating of 3 or better is considered satisfactory.

Part 4.-A surface modifier is applied to the tow of this example as follows: Ten parts of a commercial 100% polyepoxide are added to 257 parts of Water and stirred until solution is complete except for slight cloudiness. Then 133 parts of a commercial 30% silicone resin (in aqueous dispersion) are added with stirring. This emulsion is applied to 470,000 denier crimped tow of part A, the amount of emulsion applied being approximately 1 part of emulsion to parts of tow (calculated to leave 1% silicone and 0.25% epoxide on the fiber). The 'wet tow is then cut to 3- to 5-inch staple and dried by heating at 130 C. for minutes. This is identified as Fiber A-M.

Fabrics comprising the surface-modified fibers a roach those comprising the luxury animal fibers even more closely in tactility. These desirable aesthetics are durable to multiple dry cleanings and/or launderings.

EXAMPLE II Part 1.A copolymer is prepared containing 96% acrylonitrile and 4% sodium styrenesulfonate. The copolymer is dissolved in dimethylformamide to give 27% solution. The solution is spun as in Example I. The resulting filaments are washed in water at 95 C., while being drawn to 1.8 times their spun length, and passed through a chamber containing superheated steam at 130 C. where 28% relaxation occurs in 1.04 seconds under a tension of 10 mg. per denier to give filaments of 3.5 denier. The fibers, in the form of a tow with a total denier of 470,000, are crimped as in Example I, part 1, to a level of 8.6 crimps/ inch, 4.8 crimp index, in a stufiferbox crimper, and surface-modified as described in Example I, part 4.

The tow is cut into staple fiber varying in length from 3 to 5 inches. The staple is dried, and carded on a worsted card to form a sliver weighing 165 grains per yard (9.8 gm. per meter). This is identified as Fiber C-M.

A similar fiber is prepared except that the taut relaxation step is omitted. It is dried at 130 C. to result in a residual shrinkage of less than 4%. The filaments had the following properties:

Fiber C-M Fiber Without relaxation SF 0. 99 0. IS 5 125 MSF 0. 8 l. 5

8 crimper, surface-modified as described in Example I, part 4, cut into 3- to S-inch staple, and dried in a tunnel oven at 70 to C. for 15 minutes. The dried staple is processed on a worsted card to form a sliver Weighing 140 grains per yard. This is identified as Fiber DM.

Fiber C-M has a shrinkage of 1% when boiled oif Fiber D-M has a shrinkage of 27% and an SF of 0.58

Part 3.-Ten slivers of Fiber C-M are combined with 5 slivers of Fiber D-M and the combined slivers are passed through a pin drafter. Four of the resulting slivers are combined and passed through a pin drafter to form one sliver, and four of the latter type are passed through another pin drafter and finally spun into 12 cotton count yarn having 7.5 Z turns-per-inch twist. This yarn is knit on a l2-cut Jacquard knitting machine in a loose pattern (10 courses per inch). The fabric is piece-dyed at the boil using basic dyes to dye both fibers.

The dyeing operation at the boil causes the Fiber D-M to shrink and migrate to the core of the yarn and causes Fiber C-M to bulk on the surface. The finished fabric is resilient and lofty with a smooth, slick feel. The surface fibers have very little crimp. When tested for pill resistance by ASTM Test D1375, a rating of 3.0 is obtained.

Fabric prepared in the same manner but using the fiber without taut relaxation in place of Fiber C-M is less resilient and lofty, has a less smooth-slick feel and is rated 2.0 when tested for pilling resistance.

EXAMPLE III Part 1.Filaments are prepared as in Example II, part 1, except that the spun filaments are drawn to 210% of their spun length. The final denier per filament is 6, the crimp frequency 5.7/inch and crimp index 4.5. Exposure to relaxation is 1.8 seconds.

The properties of this product, Fiber E, and a similar fiber prepared without the relaxation are as follows:

Fiber E Fiber without relaxation Part 2.-Same as Example II, part 2 (Fiber D-M).

Part 3.Slivers are combined as described in Example II, part 3, and spun into a 2/9 worsted count yarn with 5 Z/2.5 S turns per inch. This yarn is knit on a 3 /2-cut Stoll knitting machine in a loose half-cardigan pattern. The fabric is piece-dyed at the boil using basic dyes. The dyeing operation causes Fiber DM to shrink and migrate to the core of the yarn and causes Fiber E to bulk on the surface. The finished fabric is soft, lofty and resilient.

EXAMPLE IV The preparation of acrylic fibers which are inherently straight, i.e., do not develop crimps and kinks in normal wetting and drying cycles, requires control of fiber tension, time of exposure and plasticizing conditions employed in the relaxation step. The composition of the acrylic polymer used to prepare the spun filaments influences the conditions required to produce inherently straight fibers.

The fibers used in the following experiments, shown in Table I, are all prepared by the process of Example I, using the indicated polymers. The resulting filaments are washed in water at C., While being drawn to the indicated extent before the relaxation step. In this table, as elsewherein the specification, the term x is employed to indicate the factor employed in drawing. For example, 3 means the fiber was drawn to 300% of its undrawn length. After relaxation, the filaments are given a mild crimp in the stutter-box crimper, then cut to staple and dried in a tunnel oven at C.

TABLE I Relaxation Conditions Properties Polymer Draw Fiber Ratio Denier Steam Tension, Time, Percent SF IS MSF Temp., O. mgJden. seconds Relax.

3X 12 102 5 300 1.09 3X 12 102 10 300 1.37 3X 12 102 30 300 1.27 3X 12 108 5 300 1.09 3X 12 108 10 300 1.14 3X 12 108 30 300 1.27

300 1.23 AN/SSS 96/4 3X 12 130 30 300 0.88 3X 12 148 5 300 0.84 3X 12 148 300 0.84 3X 12 148 30 300 0.40 2. 5X 12 130 10 1 0.82 2. 5X 12 None 0. 58 2.1 6 130 10 1 0.71 2.1 6 None 0.55 AN/MA/SSS 9315/6/04 "I i 1 0.58 5 3.75 .92 /M P -7 12 110 5 L83 EXAMPLE V stra1ght, and especially if they also have been surface Some acrylic filaments which are low in combined hydrophillic monomer do not respond to the limited steam relaxation treatments shown in Example IV as is illustrated by the first terpolymer of that example. Alternate methods for the relaxation of these acrylic filaments have been found by using the vapors from a mixture of Water and a solvent for the polymer.

The filaments for these tests, shown in Table II, are spun as in Example I, all being drawn to 2.5 times their spun length. Tows of about 1000 total denier are tensioned by attaching weights and then are exposed for 5 seconds to the vapors above boiling vessels of a 50/50 mixture of dimethylformamide and water, or an 80/20 mixture of dimethylmormamide and water. The exposed filament bundles are cut to about 3-inch lengths and dried at 130 C. The dried fibers are tested for fiber straightness factor, SF, with results shown in following table. As will be observed, these results show that a restraint of one milligram per denier is inadequate to maintain the fiber in a straight configuration in all cases. Higher restraints of 7 to 30 milligrams per denier are generally adequate modified, little change in fabric handle is produced, but if the core-fibers are not straight a rapid change in fabric handle takes place as they work up to the surface.

Measurements of fiber straightness gave the following results:

Fiber as B, Example I, but 6 denier-0.43 Fiber as D-M, Example 11, but 6 denier-05 8 EXAMPLE VII Part 1.Filaments are spun from a terpolymer consisting of 89.6% acrylonitrile, 5.7% methylacrylate and 4.7% 2-methyl-5-vinyl-pyridine. They are washed and drawn to 1.8 times their spun length and passed through a chamber containing superheated steam at 130 C. where 18% relaxation occurs in 3.75 seconds under a tension of 15 mg. per denier to give filaments of 12 denier. The tow of 470,000 denier is then crimped in a stufier-box crimper after which the tow is cut into staple fiber, varying in length from 3 to 5 inches, and dried at 130 C. This is designated fiber F and its SP is 0.92; IS is 170 and MSF is 0.3.

provided suitable plasticizing conditions are employed. In additional experiments involving other conditions of TABLE II Relaxation Polymer Tension, After exposure i0r 5 sec. to vapor over rug/denier No Taut boiling Relaxation DMF/water /50 DMF/water 80/20 1 0.65 0. 56 Polyacrylonitrile (AN 100%) ,g 0. 50 8: a 30 0. 70 0. 79

1 0 49 AN MA sss 03.6 6.0 0.4 7

IS=120, MSF=0.5. 1 IS=145, MSF=0.3.

EXAMPLE VI Fiber C-M of Example II, part 1, is compared in two blends to illustrate influence of the high-shrinkage fiber on tactile aesthetics of fabrics. This fiber is blended with a six denier-per-filament fiber otherwise the equivalent of the 3 denier-per-filament fiber described in Example I, part 2. A fabric is made from this fiber blend in the manner described in Example II, part 3. This fabric initially has a desirable soft-slick handle, but after a short period of wear (25 hours) this desirable soft-slick handle is lost. The superiority of the high-shrinkage fiber of Example II is illustrated by the fact that the fabric of that example did not lose its attractive aesthetics during wear periods of up to 350 hours.

In the low-twist bulky yarns used to prepare the fabrics of Example II and that above, some of the shrunken corefiber ends work up to the fabric surface during wear. The effect of these core-fiber ends is to dilute the straight surface-fibers. If the core-fibers themselves are relatively time, temperature and tension, additional lots of fiber are prepared. The conditions employed and SF values obtained are summarized in Table III.

Part 2.Other filaments are similarly prepared from a terpolymer consisting of 93.6% acry'lonitrile, 6.0% methyl acrylate and 0.4% sodium styrenesulfonate. The washed filaments are drawn 4.5 times their spun length yielding filaments of 3 denier. The filaments are crimped in a stutfer-box crimper then dried in a tunnel oven at 130 C. for 15 minutes. The dried tow is processed on a Turbo Stapler with a hot stretch of 1.58 at a temperature of 132 C. It is cooled, stretch-broken and lightly crimped to yield a sliver weighing 140 grains per yard (8.3 gms. per inch). This fiber (G) has a shrinkage of 30% on boilolf in water.

Part 3.Slivers of Fiber F and Fiber G are processed separately through three stages of pin drafting. The sliver weights are adjusted on the final pass so that the sliver of Fiber F weighed 14.0 grains per yard and the sliver of Fiber G weighed 6.0 grains per yard. These two slivers are combined as fed to the spinning frame to produce a 9 worsted-count yarn with Z turns per inch twist. Two ends of this yarn are plied with 2.5 S turns per inch. The plied yarn is skein dyed at the boil using both acid and basic dyes to dye both fibers. After drying, the yarn is knit on a 3 /z-cut Stoll knitting machine in a loose, novelty pattern. The skein dyeing operation at the boil causes Fiber G to shrink and migrate to the core of the yarn and causes Fiber F to bulk and form loops on the yarn surface. The finished fabric is lofty and resilient with a smooth-slick handle.

EXAMPLE VIII Filaments are spun from a copolymer of 96% acrylonitrile and 4% sodium styrenesulfonate. The spun filaments are combined into a tow of about 100,000 denier. The tow is passed through a series of tanks containing water at 95 to 98 C. During passage through the initial seven tanks, the tow is washed to a solvent level below 5% and drawn to 250% of its spun length. During the passage through the last two tanks and a coupled steam chamber at 100 to 105 C., the tow is allowed to relax in amounts varying from about 3 to about 22% of the drawn length. Experience teaches that under the conditions of this example the tension on the tow is in the range of to mg. per denier. The tow is crimped in a stutter-box crimper, cut to staple varying in length from 3 to 5 inches and dried at 130 C. The resulting staple fibers have straightness factors, SF, between 0.82 and 1.05. They are blended in the ratio of 70/30 with Fiber B of Example I and processed as in part 3 of that example to :make knit fabrics with desirable loft, resilience and smooth-slick tactile aesthetics.

EXAMPLE IX Filaments are spun from a copolymer of 96% acrylonitrile and 4% sodium styrenesulfonate. The washed filaments are drawn to 1.5 times their spun length. The wet drawn filaments are divided into three parts. One part is passed through a chamber containing superheated steam at 130 C. with tension of 10 mg. per denier to obtain 27% relaxation. The second part is passed through an apparatus consisting of a set of metering input rolls, six adjustable-speed, heated rolls and a package windup. When the temperature of the rolls is adjusted to 175 C., the speeds are adjusted to allow 26% taut relaxation. The third part is given no taut relaxation treatment. All parts are crimped mildly in a stuffer-box crimper, cut to staple of about 4-inch length, and dried at 130 C.

The straightness factors of the staple fibers are as follows:

SF No relaxation 0.62 Relaxation in steam 0.94 Relaxation on hot rolls 0.79

the fabric made from the fiber with no taut relaxation.

1 2 EXAMPLE X Part 1.A composite filament is spun by the method of U.S. Patent 3,038,236 using the following polymers:

(I) polyacrylonitrile (II) 96% acrylonitrile/4% sodium styrenesulfonate copolymer These two polymer compositions are spun together side-by-side, in about equal proportions by weight, to form a composite filament. The spun filaments are washed in hot water while being drawn to four times their spun length and dried. The dried tow has a filament denier of 6 and a total denier of 470,000. This tow is hot-stretched on the Turbo Stapler to 2.12 times its previously drawn length. When boiled off, a sample shows a shrinkage of 20%. This will be referred to as Fiber H.

Part 2.Same as described in Example II, part 1.

Part 3.-A sliver of Fiber H and a sliver of Fiber C-M are combined and run through the Hood Doubler for the purpose of blending and breaking to less than 6- inch staple. The resulting sliver comprising 60 parts of Fiber C-M and 40 parts of Fiber H is combined with four other similar slivers and run through a pin drafter. Again, four slivers are combined and passed through the pin drafter and finally spun to 20 cotton count (30 Tex) yarns of 11 Z turns per inch twist. Two of these yarns are plied and the two-ply yarn is twisted 4.7 S turns per inch. The plied yarn is knit into fabric on a 21-gauge fullfashion machine. The finished fabric weighs 7 oz./sq. yd. (234 gm./sq. meter) and has a construction of 25 (courses) X 17 (wales).

The pill resistance of this fabric is determined, by ASTM Test D-1375, to be 4.6. The fabric has a pleasant, smooth, slick feel to the hand.

EXAMPLE XI A composite filament is spun by the method of Example X using the following polymers:

(I) 100% polyacrylonitrile (II) 94.45% acrylonitrile/5.55% sodium styrenesulfonate copolymer These two polymers compositions are spun together side-by-side, in a ratio of about 3 parts of I to 1 part of II, to form a composite filament. The spun filaments are washed in hot water, drawn 2.1 times their spun length, cut to staple of 3- to 5-inch length and dried at 140 C. Other portions of the spun filaments are washed in hot water, drawn 2.5 times their spun length, cut to staple of 3- to 5-inch length and dried. The filaments in each instance are 3 denier.

Some of the filaments after drawing are passed through a chamber containing superheated steam at C. and a controlled 25% relaxation is allowed to occur.

By these variations in drawing and taut steam relaxing, composite filaments are obtained which develop different levels of crimp frequency (c.p.i.) and crimp index (C.I.) after boil-off.

(Crimp frequency is the number of crimps per inch) Crimp index= extended fiber lenght-relaxed fiber length extended fiber length X 100 Blends of these composite fibers with the Fiber C-M of Example II are made which contain 30% composite fiber. Yarns are made as described in Example II to 10 cotton count with 7.1 Z turns per inch. These yarns are knit on a 12-cut Wildman knitting machine at 15 courses per inch. The fabrics are piece-dyed at the boil using basic dyes. The dyeing operation causes the composite fibers to develop crimp which has an effect similar to shrinkage in the blend yarns.

The finished knit fabrics are compared by a panel of diverse acrylic polymers, for example non-hydrophilics judges and rated for softness and resilience with the (Example V), hydrophilics (Examples I and II), and following results shown in Table IV. All fabrics are 6.5 terpolymers (Example VI). But in every instance, it is to 7.0 oz./sq. yd. necessary to process the drawn fiber with the described TABLE IV Composite Fiber Variables Blend Fabric Ratings Fibers in Blend Spin Draw 'Iaut Steam Speed, Ratio Relaxation, Softness Resilience 2 y.p.rn. C.

70/30 Fiber DM Ex. II/Composite Fiber c.p.i.=12, C.I.=14 400 5 4 70/30 Fiber C-M Ex. 11/ Composite Fiber c.p.i.=8, O.I.= 300 5 3 70/30 Fiber C-M Ex. II/Cornposite Fiber c.p.i.=17, C.I.=19 450 2 5 Blend of Ex. 11 5 1 Ratings on basis: Soitness of woo1=0, cashmere=4. 2 Ratings on basis: Resilience of wool= 5, cashmere=2, cotton=0.

EXAMPLE XII 1o relaxation while restrained and under suitable plastic zmg conditions, which permits development of the relatively P Y 0f dcrylonltrlle dlssolved 1n dlmeihyl' straight, low-shrinkage (preferable below 5 percent) fiber. formamide are spun into fibers withacross-sectional shape Th hi h h i k fiber b d fr m the same to 21. flattened tube a 110 thickness ratio matgrials as well as others such as modacryljcs bicom. of about 3 t0 These fibers Preferred fl 20 ponents and the like. Preferably the high-shrinkage fiber plane and, therefore, do not exhibit the stiifness and resilih a hrinkage f t least 15 er nt, shrinkages being ence of fibers with a more symmetrical cross-sectional d i d b boiling i wat r fo at least 15 minutes P 0 and then drying. It should be appreciated that in the in- :Io obtain fibers with improved stiffness and resilience, Stance f bi ent shrinkage means the effect of spinnerets with a cluster of 4 small holes for each filament shortening by contraction plus shortening by developare made- T Small holes are arranged With 0118 at ment of the spiral crimp characteristic of such fibers. The writer and the other three spaqed q y and y i fibers are of the usual denier for textile applications, and cally around the center hole. Spmnerets are made in which ddition l fibers in varying amounts may be included as the diameter of the individual holes, the length to diameter long a th do not deleteriously afiect the resulting ratio of the holes, and the spacing of the holes are varied. produts These spinnerets are used to prepare fibers from a 27% It will be apparent that various changes can be made Solution in dimethylformamide of copolymer of from the detailed description of the invention without intrinsic viscosity of 96% acrylonitrile and 4% sodium departing from its scope,

styrenesulfonate. The conditions for spinning the filaments Wh i lai ed is;

are varied and the number of filaments obt ined as i- 1. A pining-resistant fabric of luxury animal fiber-like lobal shapes from the coalescing of the 4 individual properties, the fabric being fashioned of synthetic bulked streams from the cluster of holes is observed. The results rn, the yarn being made of a blend of fibers of different are shown in Table V. histories and characteristics, one of these being a high- TABLE V, SPINNING CONDITIONS 1 shrinkage, high strength, crimped fiber and generally constituting the core of the yarn, and the other being a Spinneret (30 (31mm OiHoies) goiution, o C low-shrinkage, low crimp, low strength acrylic fiber having a straightness factor of 0.70 to 1.5, an initial shrinkso 0 9e 90 100 10 8 0 age temperature of at least 145 C.., and a maximum p-t -l shrinkage force factor of no more than about 0.9, the 37 37 50 37 50 45 low strength acrylic fiber constituting principally the Code Dlam- Spacmg 3 Percent TrllobalFllaments outer sheath of the bulked yarn and at least 25 weight percent of the blend. 8%: 8% fig 3 g; 2. A bulked yarn combining the qualities of good gig 5/} g8 g8 3g 2g 2g strength, superficial smoothness and pilling resistance, 004 020 4 30 33 90 63 0 0 5 the yarn being composed of a blend of textile fibers of .88: 53 i/i g3 2; 3% 2% different characteristics non-uniformly distributed over the 4 33 47 63 83 73 63 1clgoisls-sectiorli1 gfnthehyarill, Iilr hlerelllay 1to form a $1022 of g strengt u y s run 1g -s rin age, crimpe ers Other conditions held constant included: S inning speed, 300 y. .m.; Cell temperature, 210 C.; Head temperature, %20" 0.; Spun denier? 525. and SUIT 011I1 d111g sheath f SlHOO'Eh, low-crimp and sube 1s Inert aspuatwn g s. stantially straight fibers sufiiciently weak not to support pill retention, the core and sheath blending into each The spun yarns having more than 90% trilobal filaother by a zone of intertwined fibers of both types which ments are washed in water at 95 C. while being drawn compel the yarn to move or stretch as a unit without to 2.5 times their spun length, passed through a chamber physical separation of the sheath from the core, said containing super-heated steam at 130 C. where relaxation core being made predominantly of an acrylic fiber charof 32% occurs in 3.75 seconds under tension of 10 acterized by high strength, and high shrinkage capacity,

mg. per denier to give filaments of 12 denier. The filawhile the outer sheath is composed predominantly of a ments in the form of a tow are crimped in a stutter box Weak acrylic homofiber. crimper to about 6 crimps per inch, cut to staple fiber 3. A yarn as in claim 2 in which the said fiber of the having 4-inch length and dried at 130 C. said outer sheath has in the boiled-off state a straight- When made into a yarn blend with Fiber -B and knit ness factor of 0.70 to 1.5, an initial shrinkage temperto fabric in the manner described in Example I, the knit ature of at least 145 C., and a maximum shrinkage force fabrics are more resilient than those produced in factor of no more than about 0.9 and constitutes at Example I. least 25 weight percent of the blend.

From the foregoing it is evident that the present in- 4. A bulked yarn as in claim 3 wherein the core fiber vention constitutes a significant and broad advance in prois a composite multicomponent fiber. viding synthetic fibers for applications commonly employ- S. A bulked yarn as in claim 4, the core being made ing luxurious animal fibers. From the examples it is up predominantly of .a composite filament spun sideapparent that the acrylic fiber, which upon boil-01f serves by-side from (a) polyacrylonitrile and (b) a copolymer as a relatively straight surface fiber, can be made from of acrylonitrile and sodium styrenesulfonate.

15 6. An acrylic fiber characterized in that upon boil-ofi' it has a straightness factor of 0.70 to 1.5, an initial shrinkage temperature of at least 145 C., and a maximum shrinkage force factor of no more than 0.9.

7. A fiber as in claim 6 having about 3 to 15 crimps per inch in its initial, non-boiled-off state.

8. A fiber as in claim 7 in the form of a staple.

9. An acrylic fiber blend comprising at least 25% of the staple fiber of claim 8 and the remainder a high-shrinkage fiber.

10. An acrylic fiber blend as in claim 8 wherein the high-shrinkage fiber is a composite multicomponent fiber.

11. Tow of the fiber of claim 6.

References Cited UNITED STATES PATENTS 10 STANLEY N. GILREATH, Primary Examiner.

W. H. SCHROEDER, Assistant Examiner.

U.S. Cl. XJR. 

